Baja Music Man guitar and bass onboard preamps

bajaman · Post by **bajaman** » 22 Aug 2007, 10:05

Build the original (not Ernie Ball) MusicMan preamps for Bass and Guitar.
These preamps used the programmable current LM4250 IC and consumed a very low 44uA current. I remember a Stingray owner complaining that his bass guitar was distorting - he did not even know it had a battery in it - he had been using it for at least 3 years

First up the schematics - board layout and PCB design to follow soon

The hardest part to obtain will be the 1M reverse log pot ( you could always use a !M log pot and wire it in reverse, if you cannot find one).
All the electrolytics were tantalum bead types, but I have used standard low volt aluminium types with no problems, although the tantalums had a much lower profile - the board mounted behind the tone control pots with flying leads and self adhesive double sided rubber insulation tape IIRC.
enjoy
bajaman
EDITED see later post for details

vanessa · Post by **vanessa** » 22 Aug 2007, 14:17

Thanks Baja! Did you reverse eng. your own guitars?

Know anyone who has the schemo for the 3 band eq (bass)?

-Van

trevize · Post by **trevize** » 22 Aug 2007, 16:08

Great schematic thank you!

Do you know any easily available?
Maybe a TL061 will make the battery last enough time, and could probably sound even better than the original one, what do you think?

bajaman · Post by **bajaman** » 22 Aug 2007, 20:46

Thanks Baja! Did you reverse eng. your own guitars?

No - they were both repairs - the LM4250 IC had failed - I had to break the goop covered board to identify the component values - had them for nearly 20 years - so thought it was a good idea to post them for all to see the original Leo fender (not Ernie Ball) designs.
By the Way the preamp is CRUCIAL to the sound of those old Music Man guitars and basses, as were the Alnico parallel wired humbuckers employed on them.

Know anyone who has the schemo for the 3 band eq (bass)?

NO - sorry. is that the Ernie Ball recent one

Maybe a TL061 will make the battery last enough time, and could probably sound even better than the original one, what do you think?

You could try one - just omit the 1M5 current setting resistor though, if you are using any other single dip op amp IC, BUT, you will not get the low 44uA current drain unless you use the LM4250. As for the sound difference - it will definately be a brighter top end with a fet input device like the TL061 or TL071.
cheers
bajaman

vanessa · Post by **vanessa** » 22 Aug 2007, 21:07

bajaman wrote:
Thanks Baja! Did you reverse eng. your own guitars?
No - they were both repairs - the LM4250 IC had failed - I had to break the goop covered board to identify the component values - had them for nearly 20 years - so thought it was a good idea to post them for all to see the original Leo fender (not Ernie Ball) designs.
By the Way the preamp is CRUCIAL to the sound of those old Music Man guitars and basses, as were the Alnico parallel wired humbuckers employed on them.

Now that is cool! I asked because there's a site that has a hand drawn schematic of the guitar that's messed up and is way off.

The original one that you have was refined so many times it would be hard to place what version it was unless you had a date stamp on the guitars and new the electronics to be original. Do you know what the dates were on these guitars?

In the end (I think 1978 or 79) they (Leo ad the boys) settled on what is still being used as the 2 band version. EB was the one that came up with the 3 (and up) band versions.

trevize · Post by **trevize** » 23 Aug 2007, 12:56

do you know where to find those lm4250 preamps?

bajaman · Post by **bajaman** » 23 Aug 2007, 21:31

do you know where to find those lm4250 preamps?

They are a National Semiconductors device - should be easily obtainable - I have had no problem sourcing them in New Zealand. You could always try Mouser, Digikey, RS Components, Farnell, Banzai, - Small Bear may have them.
cheers
bajaman

bajaman · Post by **bajaman** » 24 Aug 2007, 12:12

Sorry folks - there were some errors with my schems so here are the Sabre 2 guitar and Stingray bass updated schems and layouts etc.
I will post the Sabre 2 bass tomorrow
Sorry for the inconvenience

bajaman
Stingray Bass preamp
Sabre 2 Guitar preamp

bajaman · Post by **bajaman** » 25 Aug 2007, 04:02

Seymour Duncan does a nice ALNICO Music Man Stingray pickup

bajaman

bajaman · Post by **bajaman** » 25 Aug 2007, 11:19

Here is the Sabre 2 Bass preamp
Sabre 2 Bass preamp
bajaman

gus · Post by **gus** » 21 Sep 2007, 16:38

There is a web site with a lot of pictures of MM basses over the years even the preamps. I will look for it.

gus · Post by **gus** » 21 Sep 2007, 16:39

http://myweb.ecomplanet.com/TOWN8019/my ... ge0019.htm

celadine · Post by **celadine** » 21 Sep 2007, 20:29

NJR (NJM,JRC,...) makes a njm4250.

lordnielson · Post by **lordnielson** » 23 Mar 2009, 08:58

Was there ever a pcb made for these or would one use a protoboard thing ?

Jarno · Post by **Jarno** » 30 Mar 2009, 07:51

I built a stingray preamp from the small layout which is in the pictures Bajaman posted, did the toner transfer thing on Press 'n Wet and then etched and drilled the small board.
Works perfectly! Very nice tone controls, nice and thick tones to be had (as can be expected from a MM Stingray). I used a 5534, think I'll build another one with a 4250 to see if the sound differs much.

Best regards,

Jarno.

xaxxop · Post by **xaxxop** » 06 Apr 2009, 13:43

bajaman wrote:Here is the Sabre 2 Bass preamp
Sabre 2 Bass preamp
bajaman

thank you so so so so much! i love it

chicago_mike · Post by **chicago_mike** » 26 Apr 2009, 06:30

I found a bunch of the LM4250's.

So I'm building 3 for now.

But I also found the real old school military 741's I might try those as well. They kinda look like a sandwich.

Quick Q: If I use seperate volume controls for my pups, do I still need to output volume control or can that be a trimpot?

bajaman · Post by **bajaman** » 26 Apr 2009, 08:26

But I also found the real old school military 741's I might try those as well

Don't use these - they draw way too much current and your battery will go flat very quickly - stick with the LM4250 it is a miser for current in this circuit configuration - you won't even have to switch the battery on and off - it can stay connected full time - battery should last at least a year!!
bajaman

chicago_mike · Post by **chicago_mike** » 26 Apr 2009, 13:23

Gotcha! Those sound great in an mxr dist+ , just a friendly fyi, oh, and use 1n270 germaniums as well.

xaxxop · Post by **xaxxop** » 28 Apr 2009, 12:37

I have a OLP MM2 passive,i want to build it, I love stingray sound. thank you so much bajaman, but I am not sure for onboard or stompbox, because my bass haven't hole for battery

You who think?

Baja Music Man guitar and bass onboard preamps [documentation]